1. Field of the Invention
The present invention relates to a camera apparatus in which a polarization filter is capable of being turned on and off, and relates to a filter unit used for the camera apparatus.
2. Description of the Related Art
In the related art, as a camera apparatus, a camera for an outside vehicle monitoring apparatus in which a polarization filter is capable of being turned on and off has been known (for example, see JP-A-9-266572).
The camera apparatus (camera for an outside monitoring apparatus) described in JP-A-9-266572 is used to obtain external information by imaging an object outside the vehicle and performing image recognition of the imaged object in a vehicle such as an automobile.
As illustrated in FIG. 19, a camera apparatus 100 includes a CCD (charge coupled device) camera 101. The CCD camera 101 is provided with a CCD 102 as an imaging device and an objective lens system 103 is disposed on the front of the CCD 102 as an imaging optical system in which an object image is formed on an imaging surface of the CCD 102.
A polarization filter 104 that transmits only light beams having a predetermined polarization component and removes unnecessary light beams is removably provided in an optical path on the front side of the objective lens system 103.
Furthermore, a conversion lens 105 as a focus conversion lens that changes a focus distance of the objective lens system 103 is removably provided in the optical path (rear side of the objective lens system 103 in the view) of the objective lens system 103.
As described above, it is possible to prevent ghosting of a reflected image of an object inside the vehicle reflected in a front window from being incident on the objective lens system 103 and the CCD 102 by providing the polarization filter 104 in the CCD camera 101 as necessary.
Then, as illustrated in FIG. 20, the polarization filter 104 is fixed to a filter frame 107 including a worm wheel 106 in an outer peripheral portion and is rotatably mounted on a filter case 108 provided with the filter frame 107. Then, a rotation shaft 109 is provided in one end of the filter case 108 and an entirety of the filter case 108 rotates around the rotation shaft 109.
One set of bevel gears 110a and 110b connected to a drive unit such as a motor (not illustrated) are provided in the vicinity of the end portion of the filter case 108, a pinion 111 is provided in the other end of the bevel gear 110b, and the pinion 111 meshes with the worm wheel 106 of the filter frame 107. Here, a rotation shaft of the bevel gear 110a is disposed such that the shaft corresponds to the extension of the rotation shaft 109 of the filter case 108 and a rotation shaft of the bevel gear 110b is disposed perpendicularly with respect to the shaft of the rotation shaft 109.
According to such a rotation mechanism, the filter frame 107 is rotated by rotating the bevel gear 110a through the bevel gear 110b, the pinion 111, and the worm wheel 106, the polarization filter 104 can be positioned so as to have a desired polarization angle regardless of a rotational position of the filter case 108 itself, and the polarization component of the ghosting can be effectively removed.
Furthermore, the monitoring camera has a day-night switching function that performs imaging by disposing an infrared ray cut filter through which infrared rays do not pass in the front of the imaging device to match colors seen by human eyes for a bright period (daytime) and performs black-and-white imaging using the infrared rays by removing the infrared ray cut filter from the front of the imaging device for a dark period (night).